Abstract
The fundamental conditions for polarographic determination of bismuth in 1 N sulfuric acid+0.1 N hydrochldric acid solution have been investigated and applied to the analysis of cast-iron. Bismuth shows well-developed polarographic wave having about−0.11 V vs. S.C.E. of half-wave potential. This supporting electrolyte is more preferable rather than 1 N sulfuric acid alone or 1 N hydrochloric acid. Other elements except antimony in cast-iron do not interfere. Antimony is removed by volatilization with hydrobromic acid in sulfuric acid medium. Preliminary separation of bismuth in the sample is carried out at 0.3∼0.4 N acidity of nitric acid by coprecipitating with hydrous manganese dioxide, and the accompanying ferric iron is circumvented by reducing to ferrous state with hydrazine hydrochloride. The proposed method is suitable for 0.001∼0.10% of bismuth in cast-iron.
